The goals of this project are to study the physiology of the hypothalamic-pituitary-thyroid axis in normal humans, in patients with various thyroid, pituitary, hypothalamic and other diseases and in animals. Specific areas of recent and current interest have included the interaction of thyrotropin-releasing hormone (TRH) and thyroid hormones on thyrotropin (TSH) secretion, pituitary-thyroid function in patients with Graves' disease, triiodothyronine physiology and extrathyroidal thyroxine (T4) to triiodothyronine (T3) conversion and the effects of various pharmcological agents on this conversion, the subcellular distribution and physiology of brain and hypothalamic TRH and the development of methods for the measurement of TRH in biological fluids. BIBLIOGRAPHIC REFERENCES: Saberi, M., F.H. Sterling and R.D. Utiger. Reduction of extrathyroidal triiodothyronine production by propylthiouracil in man. J. Clin Invest 55:218-233, 1975. Emerson, C.H., A.J. Anderson, W.J. Howard and R.D. Utiger. The effect of iodide on serum thyroxine and triiodothyronine concentrations in hyperthyroidism. J Clin Endocrinol 40:33-36, 1975.